1. Field of the Invention
The present invention relates to a three-dimensional imaging device and a three-dimensional imaging method for obtaining two or more images to be used for three-dimensional display by imaging a subject from different positions, as well as a program for causing a computer to carry out the three-dimensional imaging method.
2. Description of the Related Art
It has been known that stereoscopic viewing using a parallax can be achieved by combining two or more images and three-dimensionally displaying the combined images. Such stereoscopic viewing can be provided by taking two or more images of the same subject from different positions using two or more cameras, and three-dimensionally displaying the two or more images by using a parallax between the subject images contained in the images.
Specifically, if the stereoscopic viewing is achieved by parallel viewing with naked eyes, the three-dimensional display can be achieved by arranging the images side by side. Further, the three-dimensional display may be achieved by combining the images, for example, by overlapping the images with providing the images with different colors, such as red and blue, or by overlapping the images with providing the images with different polarization directions. In these cases, the stereoscopic viewing can be achieved by using image separating glasses, such as red-and-blue glasses or polarization glasses, to provide a merged view of the three-dimensionally displayed images, which is attained via the automatic focusing function of the eyes (anaglyph system, polarization filter system).
The stereoscopic viewing can also be achieved without using the polarization glasses, or the like, by displaying the images on a three-dimensional display monitor which can provide stereoscopic viewing, such as a monitor of a parallax barrier system or a lenticular system. In this case, the three-dimensional display is achieved by cutting the images into vertical strips and alternately arranging the vertical strips of the images. Moreover, a system for providing the three-dimensional display by alternately displaying left and right images with changing directions of light beams from the left and right images through the use of image separation glasses or by attaching an optical element on the liquid crystal display has been proposed (scanning backlight system).
Further, stereoscopic cameras provided with two or more imaging units to carry out imaging for the above-described three-dimensional display have been proposed. This type of stereoscopic camera includes two or more imaging units disposed apart from each other by a predetermined distance and generates an image for three-dimensional display from the images obtained by the two or more imaging units. The thus generated image for three-dimensional display can be three-dimensionally displayed on a monitor. In addition, a method for use with this type of stereoscopic camera for successfully providing stereoscopic viewing by changing positions of the two or more images depending on a parallax level between corresponding areas in the two or more images has been proposed (see Japanese Unexamined Patent Publication No. 8 (1996)-009421, hereinafter “Patent Document 1”).
In the case where imaging is carried out using the stereoscopic camera, a live view image is three-dimensionally displayed on the monitor before the release button is pressed. At this time, an angle of view to be imaged can be changed using a zoom function of each imaging unit. In this case, the photographer can image a subject at a desired size by making a zoom control operation on the stereoscopic camera while viewing the three-dimensionally displayed live view image.
As described above, when the stereoscopic camera carries out a zoom operation, the angle of view is changed. During the zoom operation, the subject may often be out of focus. Further, since the stereoscopic camera includes the two or more imaging units, the zoom operation is carried out synchronously at the two or more imaging units. However, due to individual variability of a motor and a mechanism for performing the zoom function at each imaging unit, it is very difficult to achieve completely synchronous zoom operation at the imaging units. The three-dimensional display uses optical illusion to stereoscopically display the images. Therefore, when the zoom operation is carried out while the live view image is three-dimensionally displayed, the subject may be out of focus or the angle of view may vary at each imaging unit. Thus, during the zoom operation, the stereoscopic effect of the three-dimensionally displayed image may change or the stereoscopic effect may appear or disappear, and this makes it very hard to perform stereoscopic viewing.